Dependence of terahertz conductivity of CNT-based macroscale films on the CNT length and on plasma exposure time

Time-domain terahertz and infrared Fourier-transform spectroscopy techniques are used to study the conductivity mechanisms of free-standing macroscale thin films composed of disordered single-walled carbon nanotubes of two types - of various tube's lengths and films treated with oxygen plasma. We observe and analyze change in the temperature dependence of the terahertz conductance from metal-type in films with long CNTs to semiconductor-type in films with short CNTs and similar behavior of the conductance of the films with increase in the plasma exposure time.